The present invention relates to a sheet cutting device that cuts a sheet bundle and relates to an image forming system equipped with the sheet cutting device.
Up to now, there has been put to practical use a sheet finisher equipped with a sheet cutting device that aligns an edge of a sheet bundle by cutting an edge portion of the sheet bundle, for sheet bundles processed in terms of center stapling or of center folding, in the business world of printing.
Further, in recent years, there has been made an for a sheet finisher equipped with a sheet cutting device that conducts center stapling processing or center folding processing after receiving a sheet on which an image has been formed by a main body of an image forming apparatus such as a copying machine or a printer, and aligns an edge portion by cutting the edge portion of a sheet bundle with the sheet cutting device, after bookbinding, as in the case of the weekly magazines.
Many of the sheet cutting devices of this kind are those wherein a sheet bundle is fixed on a placing stand, and a cutting blade is moved for cutting operations. In this case, a position for the cutting blade to be stopped is established to be a position where a cutting edge of the cutting blade intrudes slightly into a blade receiving section that is provided on the side of the placing stand.
A stop position of the cutting edge is sometimes varied by influences of operation errors and manufacturing errors, and in this case, there are caused problems such as unfinished cutting and excessive intrusion of a cutting edge of the cutting blade into the blade receiving section.
In Unexamined. Japanese Patent Application Publication No. 2006-297535, there is disclosed a sheet cutting device wherein an electric current value of a motor that increases gradually with an increase of loads caused by striking of a blade holder against a stopper in the ca cutting sheets, detected to control the stop position for a blade. Owing to the aforesaid device, excessive force is not applied on a cutting edge, resulting in promotion of a long life.
A surface of the blade receiving section is damaged little by little, each time a bundle of sheets is cut by a cutting blade. When damage on a surface of the blade receiving section grows to be too large, cutting ability is lowered. In the sheet cutting device disclosed in Unexamined Japanese Patent Application Publication No. 006-51592, when the number of times of cutting reaches a prescribed number, the blade receiving section is shifted in the direction perpendicular to the cutting edge to renew a surface to be used of the blade receiving section, so that defective cutting that is caused by deterioration of a surface of the blade receiving section may not occur. Then, when the surface to be used of the blade receiving section becomes impossible to be renewed after being used up, the blade receiving section is replaced with a new one.
A blade and a blade receiving section of the sheet cutting device are deteriorated when cutting operations are repeated, and the blade and the blade receiving section need to be replaced for the prescribed number of cutting operations. For extending a replacement cycle of a blade by decreasing damages of the blade, it is better for the blade receiving section to be made of a softer material. However, in that case, the blade receiving section tends to be damaged easily, resulting in a short cycle of replacement of the blade receiving section. It is also possible to make a size of the blade receiving section to be large for the purpose of extending a replacement cycle for the blade receiving section. In that case, however, there is caused a problem that the device grows to be gigantic.
In the sheet cutting device described in Unexamined Japanese Patent Application Publication No. 2006-297535, there is employed construction to detect an elastic current value of a motor and thereby to stop the blade by load fluctuations in the case of striking of a holder against a stopper. However, there is no consideration about an influence on the blade receiving section, and it is feared that accurate cutting of a sheet bundle is disturbed by deterioration of the blade receiving section.
In the sheet cutting device described in Unexamined Japanese Patent Application Publication No. 2006-51592, a replacement cycle is extended by renewing a surface used of the blade receiving section. However, an object of this construction IC not using the blade receiving section effectively, and when the blade receiving section is deteriorated so early by fluctuations of a biting amount of blade receiving section of the blade, it is feared that defective cutting may be caused.